This invention relates to rotation detectors in general, and more particularly to an improved rotation detector having an electronic component containing a plurality of Hall sensors.
A rotation detector having an electronic component, associated with a magnet wheel that has an alternating North/South pole sequence, and in which the electronic component is in the form of a differential Hall IC that derives a digital signal sequence from a difference of the output signals of two Hall sensors that are displaced in phase, one behind the other, opposite the pole sequence is disclosed in the Siemens publication "Differential Hall IC's for Gear Tooth Sensing in Hostile Environments" from SENSORS, January 1989. For the purpose of accurate speed detection, in order to attain clearly defined slopes in the speed detecting digital output signal sequence even in the case of only slight changes in magnetic force which are rendered by a magnet wheel, the above publication teaches arranging two Hall sensors displaced in phase, one behind the other, on a single component for the purpose of spacing the phases of the magnet wheel; subtracting the output signals of the Hall sensors in an amplifier; and, after optionally passing through a high pass filter, converting the output signals by means of a digital signal transmitter--preferably such as a Schmitt-trigger--into a digital signal sequence which is proportional to speed or into a rotation-indicating digital signal. Although this arrangement works well, there is a requirement for increased resolution, without simultaneously increasing cost or volume requirements appreciably.